Mixing capsules which are filled with the components in separate chambers by the manufacturer are used to produce mixtures of two or more components. The components are brought into communication and mixed with one another by the user, for example by destroying a wall separating the chamber.
Mixing capsules for the production of dental materials which are often mixed from a pulverulent component and a liquid component, the mixing procedure usually talking place in a shaker unit, are known in the dental sector. The completely mixed substance is then dispensed directly onto the working area, for example into a tooth cavity, through a dispensing spout formed integrally on the mixing capsule.
DE-A-36 35 574 discloses a mixing capsule intended for the production of jointing and sealing compounds. In an illustrative embodiment described in said document, an auxiliary chamber which is present in the dispensing piston is delimited, on the side facing the main chamber of the capsule, by a foil and, on the opposite side, by an auxiliary piston which is displaceably arranged in the dispensing piston. In the initial state of the mixing capsule, in addition to the second component, a mixer body is accommodated in the auxiliary chamber, which mixer body initially serves to destroy the foil by means of manual displacement of the auxiliary piston and then assists in the mixing procedure. To allow the reduction in volume which is necessary for displacement of the inner piston together with the mixer body, a gas cushion is provided in the mixing chamber.
In a further embodiment of the known mixing capsule, the mixing body is initially situated in the main chamber. In this case, the auxiliary chamber present in the piston is closed off from the main chamber by means of a cover and on its rear side by a bellows. As a result of manual pressure being applied to the bellows, the cover is pressed away from the piston, so that the two chambers are brought into communication for the purpose of activating the capsule.
In both cases, a dedicated working step which has to be carried out manually is required for activation of the capsule. Furthermore, a gas cushion is required in order to permit the reduction in volume which is required for removal of the cover.
In a multi-component mixing capsule for dental purposes which is known from DE-U-94 00 374, a first component is contained in a mixing chamber and a second, liquid component is contained in a foil bag which is arranged in an auxiliary chamber which is separated from the mixing chamber by a displaceable wall element. A cylindrical mixing body which is present in the mixing chamber is used to displace the wall element at the start of the mixing procedure and thus to compress the foil bag, so that the latter bursts open and releases the liquid component through a liquid passage which is present in the wall element.
US 2003/0136799 discloses a mixing capsule that comprises a cartridge, a dispensing spout and a piston which is displaceably arranged in the cartridge, a sealed main chamber for receiving a first component, an auxiliary chamber which is provided in the piston and receives a second component, at least one freely movable body, and a separating device which separates the auxiliary chamber from the main chamber and through which the body can penetrate. The body is arranged in the main chamber when the separating device closed, and the auxiliary chamber and the body are designed in such a way that, during the dispensing operation, the body can pass into the auxiliary chamber as a displacement body.